1. Field of the Invention
The present invention relates to a vehicle rotary electric machine for an electric vehicle, and, more particularly, a rotary electric machine that starts an engine, assists the engine to drive wheels and regenerates electric power from running energy of a vehicle.
2. Description of the Related Art
JP-A-11-78558 proposes a vehicle rotary electric machine (hereinafter referred to as the vehicle-rear rotary electric machine) including a rotor connected between an engine and a gear transmission to be driven by a crank shaft.
The conventional vehicle-rear rotary electric machine makes it possible to mount various belt-driven accessories in front of the engine along a belt, which prevents a pulley of a small diameter from slipping thereon.
However, such a vehicle-rear rotary electric machine has a long power train between a crankshaft and a torque transmission mechanism. The power train includes a clutch disposed at the back of the crankshaft and a torque converter. Therefore, the power train with its housing needs a large mounting space, which may increase a body vibration.
Therefore, it is an object of the present invention to solve the above-described problems and to provide a compact, light-weight, and high power vehicle-rear-type rotary electric machine.
Such a vehicle-rear-type rotary electric machine (hereinafter referred to as the rear-type machine or the machine) is connected coaxially with a crankshaft. The rear-type machine has a cylindrical stator, a rotor having, an inner rotor portion and an outer rotor portion respectively disposed at opposite peripheral sides of the stator, and a stator winding having a set of multi-phase windings for electro-magnetically connecting with both the rotor portions.
Further, the axial length of the machine can be decreased to about a half thereof. The axial length of the space between the back of the engine and the torque transmission mechanism is reduced to make the power train compact. This naturally restrains vibration of the power train.
If the above inner and outer rotor portions overlap each other in the radial direction, the radial length of the machine increases. However, this increases the flywheel effect of the machine, so that any additional rotary-inertia-member for the flywheel effect can be omitted. In other words, the rotor of the machine according to the invention has a part of or all of the flywheel effect.
The inertia mass of the flywheel is proportional to a square of the mean value of the radius of the flywheel. Therefore, the flywheel effect per weight of the rotor of the machine that has two-radially-combined-rotor-type structure can be drastically improved as compared with the machine that has the single-rotor-type structure.
Moreover, because the opposite peripheral surfaces of a single stator are used for magnetic connection, the core back can be used as a common yoke for the magnetic path of the two rotor portions. This can make the stator more compact and lighter.
Because two rotating magnetic fields generated by the two rotor portions interlink the stator winding, it is possible to shorten the coil ends of the stator winding as compared with a rotary electric machine having respective stators for respective rotor portions.
Moreover, because magnetic fluxes generated by different rotor portions, it is possible to provide a machine that has a combined characteristic of two rotary electric machines.
According to another feature of the invention, the machine further includes a bowl member that connects the torque transmission mechanism and a crank shaft. Therefore, it is not necessary to provide an additional frame for supporting two rotor portions.
According to another feature of the invention, a annular portion supports a larger cylindrical member that supports the outer rotor portion and connects a connecting disk with the transmission mechanism. Therefore, the shape can be simplified, the size and weight can be reduced, and an excellent linkage with the torque transmission mechanism can be provided.
According to another feature of the invention, the stator core has a core back at the radial center thereof. Therefore, the stator core can be made compact and light.
According to a further feature of the invention, each set of the phase windings is wound on one of opposite surfaces of the stator to form a U-shaped cross-section in the circumferential and axial directions. Therefore, the structure and manufacture of the stator can be simplified. In particular, each phase winding is manufactured in the U-shape beforehand so that each can be readily inserted into the inner and outer slot.
According to another feature of the invention, each of the phase windings is wound to form a square cross-section. Therefore, the structure and the manufacture of the stator can be made simple.
Further, each of the phase windings is wound in a toroidal shape (square in cross-section), invalid length per one-turn coil can be made equal to the length a wire passing along opposite ends of the stator core. Therefore, the wire length of the winding can be drastically reduced, the weight of the copper wire can be reduced, and the efficiency thereof can be increased.
According to another feature of the invention, each of the phase windings is wave-wound at approximately the same slot pitches as the magnetic pole pitches so that current flowing at the slot formed at the inner surface and current flowing the slots formed at the outer surface are opposite to each other. Therefore, the stator can be made simple in structure, and the winding can be carried out by a winding machine.
According to another feature of the invention, each of the rotor portions has a rotor-structure having permanent magnets.
According to another feature of the invention, both the rotor portions have a squirrel-cage structure. Therefore, a highly strong and durable rotor can be manufactured at low cost. Moreover, it is possible to control the output voltage from the stator while the engine is operating. Even if the control can not be made, the output voltage does not become too high without providing control means (which needs high voltage insulation).
According to a further feature of the invention, each of the rotor portions has a reluctance-type-rotor-structure. Therefore, the rotor can be manufactured at a low cost.
According to a further feature of the invention, the inner rotor portion has a permanent-magnet-rotor-structure, and the outer rotor portion has a reluctance-type-rotor-structure. Therefore, the output power of the inner rotor portion, which has a small electromagnetic connection area and a small circumferential speed, can be increased, and the drawback of the low-power reluctance rotor can be compensated by a large diameter of the outer rotor.
According to another feature of the invention, the circumferentially central portion of a magnetic salient pole of the reluctance-type-rotor-structure is disposed at a position an electric angle 45xc2x0-90xc2x0 in advance of the circumferentially central portion of a magnetic pole of the permanent-magnet-type-rotor-structure in the rotation direction.
Therefore, the resultant torque and output power can be increased.
According to another feature of the invention, the stator is fixed to the housing by a supporting rod member that is force-fitted to the core back in the axial direction. Therefore, the supporting rod member achieves both to compress the stator core made of laminated iron sheets in the lamination direction and to fix the stator to the housing, without decreasing the area of both surfaces of the electromagnetic connection of the stator core.
According to another feature of the invention, one end of both the rotor portions has a permanent-magnet type-rotor-structure, and the other end of both the rotor portions has a field-coil-type rotor-structure. Therefore, the generation and motor characteristics of the machine can be controlled by the field current control.
According to another feature of the invention, one of the rotor portions is a permanent magnet rotor, and the other is an induction type rotor portion having magnetic poles. A field coil is wound on a stationary yoke to alternately magnetize the magnetic poles of the induction type rotor. Therefore, it is not necessary to mount the field coil in the rotor portion. This increases resistance to the centrifugal force and simplifies the field current circuit.
According to another feature of the invention, the machine further includes a control unit for controlling the current of the stator winding by inverting field current. Therefore, at a high speed rotation, even if one of the rotor portions generates a high voltage, the other rotor portion having the field coil type rotor structure generates an inverse voltage so as to prevent unnecessary output voltage of the stator winding.
According to further feature of the invention, the slots formed at the outer surface and at the inner surface are disposed at the same circumferential positions at opposite sides of the core back. In addition, the magnetic poles of the inner rotor portion and the outer rotor portion that are disposed at the circumferentially the same position are polarized in the opposite direction.
Therefore, most of the magnetic fluxes pass a large magnetic path going to and coming from one of the rotor portions, so that the magnetic fluxes passing the core back can be reduced, thereby, to control the iron loss and magnetic saturation.
According to another feature of the invention, the slots formed at the outer surface and the inner surface are disposed at opposite side of the core back and shifted from each other at half slot pitch in the circumferential direction. Therefore, average radial width of the core back increases to prevent the iron loss and magnetic saturation as well as to make the stator core thinner and more compact.
It is another object of the present invention to provide a low-noise and low vibration vehicle rotary electric machine.
According to a further feature of the invention, a vehicle rotary electric machine includes a rotor for transmitting torque to a vehicle shaft and a stator having a peripheral surface opposite circumference of the rotor and fixed to a housing. The rotor includes an outer rotor portion having an inner surface electro-magnetically connected to the outer surface of the stator, an inner rotor portion fixed to the outer rotor portion and having an outer surface electro-magnetically connected to the inner surface of the stator. The stator includes a stator core disposed between the inner rotor portion and the outer rotor portion and a stator winding having a set of multi-phase windings wound on the stator core for electro-magnetically connecting with both the rotor portions. The stator core has a plurality of outer slots-and-teeth formed in the outer peripheral surface thereof at certain pitches and a plurality of inner slots-and-teeth formed in the inner peripheral surface thereof at certain pitches. Each of the inner peripheral surface on the outer rotor portion and the outer peripheral surface of the inner rotor portion has a salient pole portion having a small magnetic reluctance. When the circumferential center of the salient pole portion of the outer rotor portion and the circumferential center of the outer slot opening of the stator core are disposed at the same angular position, the circumferential center of the salient pole portion of the inner rotor portion and the circumferential center of the inner slot opening of the stator core are shifted from each other at an interval that is equal to or less than xc2xc of a slot-pitch.
Regarding the magnetic pole portion of the outer rotor portion and the outer slots of the stator, the circumferential component of the magnetic force generated between the above two causes a reluctance torque. This radial component of the magnetic force gives the teeth a tensile force acting toward the magnetic pole portion. The radial component of the magnetic force, because of the slot openings of the outer slots of the stator, changes at a cycle equal to the time of one pole-pitch rotation. This causes vibration and noises. In the same manner, a cyclic change of the radial component of the magnetic force between the inner rotor portion and inner slots causes vibration and noises.
It has been noted that the radial components of two electro-magnetic forces acting on the outer periphery inside the stator are opposite to each other. The phase angle between two is controlled to balance the radial components of the two magnetic forces to reduce the above-stated vibration and noises.
When the radial component of a maximum electro-magnetic force is given to the outer teeth of the stator from the magnetic pole portion of the outer rotor portion, the radial component of a maximum electro-magnetic force is given to the inner teeth of the stator from the magnetic pole portion of the inner rotor portion. At this time, the stator is pulled radially outward at a maximum force by the magnetic pole portion of the outer rotor portion. At the same time, it is also pulled radially inward by the magnetic pole portion of the inner rotor portion, so that the radial shift of the stator can be balanced.
When the circumferential center of the magnetic salient pole of the outer rotor portion and the circumferential center of the outer slot opening of the stator core are positioned at the same angular position, the circumferential center of the magnetic salient pole of the inner rotor portion and the circumferential center of the inner slot opening of the stator core are positioned at the same angular position.
It is clear that the combined force of the ripple of the radial component of the two electro-magnetic forces that act on the inner and outer peripheries of the stator decreases even if the phase of the above two is different from each other. If the cycle corresponds to one-slot pitch is 2xcfx80, it is clear that the phase difference between two is a value between xe2x88x922xcfx80(xe2x88x92xc2xc slot-pitch) and +2xcfx80(+{fraction (1/4)} slot-pitch).
According to another feature of the invention, the circumferential center of the magnetic salient pole of the outer rotor portion and the circumferential center of the magnetic salient pole of the inner rotor portion are positioned at the same angular position within a normal production tolerance. The circumferential center of the outer slot opening of the stator core and the circumferential center of the inner slot opening of the stator core are positioned at the same angular position within a normal production tolerance. The outer slots and the inner slots that are positioned at the same angular position respectively accommodate conductors of the same phase but of opposite direction.
Thus, the angular position of both rotor portions of the magnetic salient poles is the same. As a result, the angular position of the teeth of the inner and outer peripheries of the stator is the same. Therefore, the radial component of the above electro-magnetic force acting on the outer teeth and the radial component of the above electro-magnetic force inversely acting on the inner teeth appears at the same angular position in the direction opposite to each other and in the same magnitude.
According to another feature of the invention the outer slots and the inner slots that are positioned at the same angular position accommodate a concentration-wound stator winding.
Therefore, it is easy to wind the coils, and the coil ends become smaller so that a small and high powered rotary electric machine can be provided.
According to another feature of the invention, concentrate-wound coils are wound around respective pairs of outer and inner slots of cylindrical stator core disposed at the same angular position, and a pair of rotor portions is disposed to respectively face both the peripheral surfaces.
Therefore, concentrate coils can be easily mounted in each pair of inner and outer slots disposed at the same angular position without dividing the stator core into pieces, so that the length of coil ends thereof extending in the radial direction can be reduced to the minimum. In addition, a pair of axially extending portion of each concentrate-wound coil electro-magnetically connects both the outer and the inner rotor portions to generate torque. As a result, axial length of the stator can be drastically reduced by reduction in the axial length of the coil end and by utilizing both peripheral surfaces of the stator core.
It is another object of the invention is to provide a radial-air-gap-type vehicle rotary electric machine having one-end-support structure that is excellent in cooling the rotor, stator and the rotor frame.
According to another feature of the invention, a stator core is fixed to the housing at the side opposite a rotor frame, and a rotor frame has a gap between the stator and the rotor frame and an air inlet for conducting air from outside to the gap. In other words, the rotor frame has an air inlet for conducting air from outside to a radially extending gap between the stator and the rotor frame.
It is a further object of the invention is to provide a one-end-supported radial-air-gap-type rotary electric machine that is easy to fix and position.
In the rotary electric machine according to another feature of the invention, a stator core is supported to a housing at its one end by a plurality of support pins that are respectively force-fitted to axial holes formed in the stator core and inserted and fixed to a plurality of through holes formed at radial wall of the housing. In other words, a plurality of support pins are force-fitted into the core-back of stator core in the axial direction, and one end of each the support pin is inserted to a through hole of a radial wall of the housing to support the stator core by the housing at one end thereof.
Thus, fixing and positioning works of the stator core can be made much easier than those by through bolts inserted into through holes of the stator core. Therefore, accurate centering of the stator core can be carried out only by the support pins being inserted into the through hole of the radial wall.
Preferably, provisional holes, which are slightly smaller than the through holes of the stator core, are formed when core sheets are punched out. The provisional through holes are formed into the through holes when the core sheets are laminated.